Dependence of muscleV˙o 2on blood flow dynamics at onset of forearm exercise

1996 ◽  
Vol 81 (4) ◽  
pp. 1619-1626 ◽  
Author(s):  
R. L. Hughson ◽  
J. K. Shoemaker ◽  
M. E. Tschakovsky ◽  
J. M. Kowalchuk
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Venous Blood ◽  
Lactate Concentration ◽  
Flow Dynamics ◽  
Cross Sectional ◽  
Mean Response Time ◽  
Rate Of Increase ◽  
Blood Flow Dynamics ◽  
Forearm Exercise

Hughson, R. L., J. K. Shoemaker, M. E. Tschakovsky, and J. M. Kowalchuk. Dependence muscle ofV˙o 2on blood flow dynamics at the onset of forearm exercise. J. Appl. Physiol. 81(4): 1619–1626, 1996.—The hypothesis that the rate of increase in muscle O2 uptake (V˙o 2 mus) at the onset of exercise is influenced by muscle blood flow was tested during forearm exercise with the arm either above or below heart level to modify perfusion pressure. Ten young men exercised at a power of ∼2.2 W, and five of these subjects also worked at 1.4 W. Blood flow to the forearm was calculated from the product of blood velocity and cross-sectional area obtained with Doppler techniques. Venous blood was sampled from a deep forearm vein to determine O2 extraction. The rate of increase inV˙o 2 musand blood flow was assessed from the mean response time (MRT), which is the time to achieve ∼63% increase from baseline to steady state. In the arm below heart position during the 2.2-W exercise, blood flow andV˙o 2 musboth increased, with a MRT of ∼30 s. With the arm above the heart at this power, the MRTs for blood flow [79.8 ± 15.7 (SE) s] and V˙o 2 mus(50.2 ± 4.0 s) were both significantly slower. Consistent with these findings were the greater increases in venous plasma lactate concentration over resting values in the above heart position (2.8 ± 0.4 mmol/l) than in the below heart position (0.9 ± 0.2 mmol/l). At the lower power, both blood flow andV˙o 2 musalso increased more rapidly with the arm below compared with above the heart. These data support the hypothesis that changes in blood flow at the onset of exercise have a direct effect on oxidative metabolism through alterations in O2transport.

Peripheral circulatory factors limit rate of increase in muscle O2 uptake at onset of heavy exercise

2001 ◽  
Vol 90 (1) ◽  
pp. 83-89 ◽  
Author(s):  
Maureen J. MacDonald ◽  
Heather L. Naylor ◽  
Michael E. Tschakovsky ◽  
Richard L. Hughson
Keyword(s):  
Blood Flow ◽  
Forearm Blood Flow ◽  
Muscle Blood Flow ◽  
Venous Blood ◽  
Lactate Concentration ◽  
Exercise Bout ◽  
Handgrip Exercise ◽  
Acid Base ◽  
Rate Of Increase ◽  
Forearm Exercise

We used an exercise paradigm with repeated bouts of heavy forearm exercise to test the hypothesis that alterations in local acid-base environment that remain after the first exercise result in greater blood flow and O2 delivery at the onset of the second bout of exercise. Two bouts of handgrip exercise at 75% peak workload were performed for 5 min, separated by 5 min of recovery. We continuously measured blood flow using Doppler ultrasound and sampled venous blood for O2 content, Pco 2, pH, and lactate and potassium concentrations, and we calculated muscle O2uptake (V˙o 2). Forearm blood flow was elevated before the second exercise compared with the first and remained higher during the first 30 s of exercise (234 ± 18 vs. 187 ± 4 ml/min, P < 0.05). Flow was not different at 5 min. Arteriovenous O2 content difference was lower before the second bout (4.6 ± 0.9 vs. 7.2 ± 0.7 ml O2/dl) and higher by 30 s of exercise (11.2 ± 0.7 vs. 10.8 ± 0.7 ml O2/dl, P < 0.05). Muscle V˙o 2was unchanged before the start of exercise but was elevated during the first 30 s of the transition to the second exercise bout (26.0 ± 2.1 vs. 20.0 ± 0.9 ml/min, P < 0.05). Changes in venous blood Pco 2, pH, and lactate concentration were consistent with reduced reliance on anaerobic glycolysis at the onset of the second exercise bout. These data show that limitations of muscle blood flow can restrict the adaptation of oxidative metabolism at the onset of heavy muscular exertion.

Muscle Blood-Flow Dynamics at Exercise Onset

2006 ◽  
Vol 38 (10) ◽  
pp. 1811-1818 ◽  
Author(s):  
MICHAEL E. TSCHAKOVSKY ◽  
NATASHA R. SAUNDERS ◽  
KATHERINE A. WEBB ◽  
DENIS E. O'DONNELL
Keyword(s):  
Blood Flow ◽  
Muscle Blood Flow ◽  
Flow Dynamics ◽  
Exercise Onset ◽  
Blood Flow Dynamics

Alveolar oxygen uptake and femoral artery blood flow dynamics in upright and supine leg exercise in humans

1998 ◽  
Vol 85 (5) ◽  
pp. 1622-1628 ◽  
Author(s):  
Maureen J. MacDonald ◽  
J. Kevin Shoemaker ◽  
Michael E. Tschakovsky ◽  
Richard L. Hughson
Keyword(s):  
Blood Flow ◽  
Oxygen Uptake ◽  
Femoral Artery ◽  
Supine Position ◽  
Knee Extension ◽  
Mean Response Time ◽  
Rate Of Increase ◽  
Blood Flow Dynamics ◽  
Leg Exercise ◽  
Alveolar Oxygen

We tested the hypothesis that the slower increase in alveolar oxygen uptake (V˙o 2) at the onset of supine, compared with upright, exercise would be accompanied by a slower rate of increase in leg blood flow (LBF). Seven healthy subjects performed transitions from rest to 40-W knee extension exercise in the upright and supine positions. LBF was measured continuously with pulsed and echo Doppler methods, andV˙o 2 was measured breath by breath at the mouth. At rest, a smaller diameter of the femoral artery in the supine position ( P < 0.05) was compensated by a greater mean blood flow velocity (MBV) ( P < 0.05) so that LBF was not different in the two positions. At the end of 6 min of exercise, femoral artery diameter was larger in the upright position and there were no differences inV˙o 2, MBV, or LBF between upright and supine positions. The rates of increase ofV˙o 2 and LBF in the transition between rest and 40 W exercise, as evaluated by the mean response time (time to 63% of the increase), were slower in the supine [V˙o 2 = 39.7 ± 3.8 (SE) s, LBF = 27.6 ± 3.9 s] than in the upright positions (V˙o 2 = 29.3 ± 3.0 s, LBF = 17.3 ± 4.0 s; P < 0.05). These data support our hypothesis that slower increases in alveolarV˙o 2 at the onset of exercise in the supine position are accompanied by a slower increase in LBF.

scholarly journals Nephron blood flow dynamics measured by laser speckle contrast imaging

2011 ◽  
Vol 300 (2) ◽  
pp. F319-F329 ◽  
Author(s):  
Niels-Henrik Holstein-Rathlou ◽  
Olga V. Sosnovtseva ◽  
Alexey N. Pavlov ◽  
William A. Cupples ◽  
Charlotte Mehlin Sorensen ◽  
...  
Keyword(s):  
Blood Flow ◽  
Signal Transmission ◽  
Experimental Studies ◽  
Flow Dynamics ◽  
Laser Speckle ◽  
Tubuloglomerular Feedback ◽  
Contrast Imaging ◽  
Laser Speckle Contrast Imaging ◽  
Speckle Contrast ◽  
Blood Flow Dynamics

Tubuloglomerular feedback (TGF) has an important role in autoregulation of renal blood flow and glomerular filtration rate (GFR). Because of the characteristics of signal transmission in the feedback loop, the TGF undergoes self-sustained oscillations in single-nephron blood flow, GFR, and tubular pressure and flow. Nephrons interact by exchanging electrical signals conducted electrotonically through cells of the vascular wall, leading to synchronization of the TGF-mediated oscillations. Experimental studies of these interactions have been limited to observations on two or at most three nephrons simultaneously. The interacting nephron fields are likely to be more extensive. We have turned to laser speckle contrast imaging to measure the blood flow dynamics of 50–100 nephrons simultaneously on the renal surface of anesthetized rats. We report the application of this method and describe analytic techniques for extracting the desired data and for examining them for evidence of nephron synchronization. Synchronized TGF oscillations were detected in pairs or triplets of nephrons. The amplitude and the frequency of the oscillations changed with time, as did the patterns of synchronization. Synchronization may take place among nephrons not immediately adjacent on the surface of the kidney.

Failure of prostaglandins to modulate the time course of blood flow during dynamic forearm exercise in humans

1996 ◽  
Vol 81 (4) ◽  
pp. 1516-1521 ◽  
Author(s):  
J. K. Shoemaker ◽  
H. L. Naylor ◽  
Z. I. Pozeg ◽  
R. L. Hughson
Keyword(s):  
Blood Flow ◽  
Brachial Artery ◽  
Time Course ◽  
Forearm Blood Flow ◽  
Voluntary Contraction ◽  
Double Blind ◽  
Rate Of Increase ◽  
Forearm Exercise ◽  
Blind Manner ◽  
Exercise In Humans

Shoemaker, J. K., H. L. Naylor, Z. I. Pozeg, and R. L. Hughson. Failure of prostaglandins to modulate the time course of blood flow during dynamic forearm exercise in humans. J. Appl. Physiol. 81(4): 1516–1521, 1996.—The time course and magnitude of increases in brachial artery mean blood velocity (MBV; pulsed Doppler), diameter ( D; echo Doppler), mean perfusion pressure (MPP; Finapres), shear rate (γ˙ = 8 ⋅ MBV/ D), and forearm blood flow (FBF = MBV ⋅ π r 2) were assessed to investigate the effect that prostaglandins (PGs) have on the hyperemic response on going from rest to rhythmic exercise in humans. While supine, eight healthy men performed 5 min of dynamic handgrip exercise by alternately raising and lowering a 4.4-kg weight (∼10% maximal voluntary contraction) with a work-to-rest cycle of 1:1 (s/s). When the exercise was performed with the arm positioned below the heart, the rate of increase in MBV and γ˙ was faster compared with the same exercise performed above the heart. Ibuprofen (Ibu; 1,200 mg/day, to reduce PG-induced vasodilation) and placebo were administered orally for 2 days before two separate testing sessions in a double-blind manner. Resting heart rate was reduced in Ibu (52 ± 3 beats/min) compared with placebo (57 ± 3 beats/min) ( P < 0.05) without change to MPP. With placebo, D increased in both arm positions from ∼4.3 mm at rest to ∼4.5 mm at 5 min of exercise ( P < 0.05). This response was not altered with Ibu ( P > 0.05). Ibu did not alter the time course of MBV or forearm blood flow ( P > 0.05) in either arm position. The γ˙ was significantly greater in Ibu vs. placebo at 30 and 40 s of above the heart exercise and for all time points after 25 s of below the heart exercise ( P < 0.05). Because PG inhibition altered the time course ofγ˙ at the brachial artery, but not FBF, it was concluded that PGs are not essential in regulating the blood flow responses to dynamic exercise in humans.

Investigation of blood flow dynamics by NMR angiography

1990 ◽  
Vol 8 (2) ◽  
pp. 167-172 ◽  
Author(s):  
Q. Guo ◽  
L. Friloux ◽  
O. Nalcioglu
Keyword(s):  
Blood Flow ◽  
Flow Dynamics ◽  
Blood Flow Dynamics

scholarly journals Sequential alterations in the diameters of capillaries in rabbit skeletal muscle following deep transverse friction - a morphometric study

2005 ◽  
Vol 61 (2) ◽  
Author(s):  
M. A. Gregory ◽  
M. N. Deane ◽  
M. Marsh
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Blood Flow ◽  
Biceps Femoris ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Biceps Femoris Muscle ◽  
Beneficial Effects ◽  
The Cross

Objective: The precise mechanisms by which massage promotes repair in injured soft tissue are unknown. Various authorshave attributed the beneficial effects of massage to vasodilation and increased skin and muscle blood flow. The aim of this study was to determine whether deep transverse friction massage (DTF) causes capillary vasodilation in untraumatised skeletal muscle. Setting: Academic institution.Interventions: Twelve New Zealand white rabbits were anaesthetised and the left biceps femoris muscle received 10 minutes of DTF. Following treatment, wedge biopsies were taken from the musclewithin 10 minutes of treatment (R1 - 4), 24 hours (R5 - 8) and 6 days(R9 - 12) after treatment. To serve as controls, similar biopsies weretaken from the right biceps femoris of animals. The samples were fixed, dehydrated and embedded in epoxy resin.Transverse sections (1µm) of muscle were cut, stained with 1% aqueous alkaline toluidine blue and examined with a light microscope using a 40X objective. Images containing capillaries were captured using an image analyser with SIS software and the cross sectional diameters of at least 60 capillaries were measured from each specimen. Main Outcome Measures: Changes in capillary diameter. Results: The mean capillary diameters in control muscle averaged 4.76 µm. DTF caused a significant immediate increase of 17.3% in cross sectional area (p<0.001), which was not significantly increased by 10.0% after 24 hours (p>0.05). Six days after treatment the cross-sectional area of the treated muscle was 7.6% smaller than the controls. Conclusions: This confirms the contention that DTF stimulates muscle blood flow immediately after treatment and this may account for its beneficial effects in certain conditions. 

scholarly journals Changes in lower extremity blood flow during advancing phases of pregnancy and the effects of special footwear

2017 ◽  
Vol 16 (3) ◽  
pp. 214-219 ◽  
Author(s):  
Marta Gimunová ◽  
Martin Zvonař ◽  
Kateřina Kolářová ◽  
Zdeněk Janík ◽  
Ondřej Mikeska ◽  
...  
Keyword(s):  
Blood Flow ◽  
Venous Blood ◽  
Cross Sectional Area ◽  
Popliteal Vein ◽  
Control Group ◽  
Venous Disease ◽  
Venous Blood Flow ◽  
Sectional Area ◽  
Cross Sectional ◽  
Experimental Group

Abstract Background During pregnancy, a number of changes affecting venous blood flow occur in the circulatory system, such as reduced vein wall tension or increased exposure to collagen fibers. These factors may cause blood stagnation, swelling of the legs, or endothelial damage and consequently lead to development of venous disease. Objectives The aim of this study is to evaluate the effect of special footwear designed to improve blood circulation in the feet on venous blood flow changes observed during advancing phases of pregnancy. Methods Thirty healthy pregnant women participated in this study at 25, 30, and 35 weeks of gestation. Participants were allocated at random to an experimental group (n = 15) which was provided with the special footwear, or a control group (n = 15). At each data collection session, Doppler measurements of peak systolic blood flow velocity and cross-sectional area of the right popliteal vein were performed using a MySonoU6 ultrasound machine with a linear transducer (Samsung Medison). The differences were compared using Cohen’s d test to calculate effect size. Results With advancing phases of pregnancy, peak systolic velocity in the popliteal vein decreased significantly in the control group, whereas it increased significantly in the experimental group. No significant change in cross-sectional area was observed in any of the groups. Conclusions Findings in the experimental group demonstrated that wearing the footwear tested may prevent venous blood velocity from reducing during advanced phases of pregnancy. Nevertheless, there is a need for further investigation of the beneficial effect on venous flow of the footwear tested and its application.

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